Hello reader, I have an exam really soon and it includes a good bit of trigonometry, but I'm having problems with the trig stuff because this exam does not allow calculators and since I was dependent on the calculator, I haven't memorized anything about the trigonometric functions. I don't know the basic angles trigonometry and I don't know when they are positive or negative , etc. I basically want the method to master trigonometric functions in terms of what I need to memorize (and if there's something else to study as well). What do I need to know for the exam? And another thing. This is a sample question : Find x ∈ [0, π/2] such that : cos^2 2x − 3 sin^2 2x = 0 I don't even know where to start when solving this thing, and will greatly appreciate a method of solving this type of questions and maybe some other examples like this. Thank you in advance.